In the related art, in a membrane type cryogenic tank including a membrane in which a plurality of membrane panels are welded, in order to maintain a shape of a thin membrane having low stiffness, a configuration which is supported to be pressed to a concrete wall via a heat insulating material by a membrane anchor mechanism is used (for example, refer to Japanese Examined Patent Application, Second Publication No. S63-23440). As the membrane type cryogenic tank, tanks having various shapes are used, and for example, a tank which is formed to have a square corner portion, a cylindrical corner portion, or the like is also used widely. In Japanese Unexamined Patent Application, First Publication No. 2009-79736, a membrane anchor mechanism which supports a membrane panel (corner membrane panel) installed in a corner portion of a cryogenic tank is disclosed. The membrane anchor mechanism disclosed in Japanese Unexamined Patent Application, First Publication No. 2009-79736 is installed at a boundary portion of a haunch structural portion provided on a corner portion, and supports an edge portion of the corner membrane panel.